You can calculate the developed length of sheet metal parts using bend calculation tables.
With bend calculation tables, you can define different angular ranges, assign equations to those ranges, and calculate the developed length of the part.
The default location for bend calculation tables is install_dir\lang\english\Sheetmetal Bend Tables.
Example of a bend calculation table:

Column A 
Displays the variables that can be used in equations: s = material thickness
 r = bend radius
 kfactor = kfactor (you can use an equation or a value)
 ß = aperture angle

Angular Range 
Lets you define the angular ranges. The angular range defines the different ranges that must be used for specific calculations.

You define the smallest angular value of a range to the left of ß
 ß = angle variable
 You define the largest angular value of a range to the right of ß

Equation 
Lets you define the equation to use for the angular range. You can also use a constant value. 
use tangent length 
Lets you determine the method to calculate flanges: virtual sharp or tangent length. The equation that calculates developed length is: LD = A + B + V, where V can be negative. When V is negative, it is the same as using bend deduction, even though the equation is for bend allowance.

Bend Calculation Examples
Angular Range 
Example 
0 <= ß <= 90 
Tangent length = Yes

90 < ß <= 165 
Tangent length = No

165 < ß <= 180 
Tangent length = No
